Rotary devices and casing structures therefor



Feb. 17, 1959 H. R. NILSSON 2,873,909

ROTARY DEVICES AND CASING STRUCTURES THEREFOR Filed'oct. 26, 1954 4Sheets-Sheet 1 Feb. 17, 1959 H; R. NILSSON 2,87

ROTARY DEVICES AND CASING STRUCTURES THEREFOR Filed 061;. 26, 1954 4Sheets-Sheet 2 Feb. 17, 1959 H. R. NILSSON 2,873,909

ROTARY DEVICES AND CASING STRUCTURES THEREFOR 4 Sheets-Sheet 5 FiledOct. 26, 1954 Feb. 17, 1959 H. R. NILSSON I 2,873,909

ROTARY DEVICES AND CASING STRUCTURES THEREFOR Filed Oct. 26. 1954 4Sheets-Sheet 4 IU'IIIH llll Unite Sttes Patent 2,873,909 v ROTARYDEVICES AND CASING STRUCTURES Hans Robert Nilssom Ektor-p, Sweden, assignorgby mesne 1 assignments, tou svenska lRotor'fMasRiner iAktiebolag,

Nacka, Sweden, a .corporationzofisweden Application oeoberizsprss'q,Serial N 4587 7*Clain 1s. (Cl."-.230i'i'143) Thepresent inventionrelates to a casin'gstructurefor' a rotary device of thekindproviding,Woikingfspaces..or chambers 'between .iinterme'shing. rotors''oft the (screw wheel type. Such devices may'be employed ascompressorsto-compressa gaseousifiilid orflas enginesgen'era ting power by theexpansion- .of.fsuch fluid. Morespecificall-y, the invention relates .toaicasing structure for sucha device, having at :least .two. intersectingI parallel bores for a corresponding number of parallel rotors providedwith intermeshing helical lobes .and grooves and [mounted to rotate insaid bores.

. .One object .of .the invention .is,;to :provide a casing structurepermitting. relative expansions of different parts of :the rotary device.due .to temperature differences .during .the .operationnof the samewithout warping-of the casing or derangement of the .close running .fit.between the rotors andthe boresenvelopingthe same;

Another objectof the invention is toprovideacasing structure in whichonlythe parts thereof :CXPOSEdZtOShigh temperatures :or wear aremadeof a.high resistant rnaterial such as steel and which is-comparativelyexpensive while the rest of thecasingfis made ofa cheaper andnotso'resistant material. Inthis respect the invention contemplates theuseof a light weightmaterial such as light metals or light metal alloysin order torreduce the total=weightof theacomplete rotary device withoutaffecting its performance.

2373,9119 Patented Feb. 17, 1959 "ice . 2 a Fig. 3 is an end view of thecasing structuretaken in projection on the line 3- 3 ofFig. 2.

, Fig. 4 is a horizontal longitudinal section of the-casingstructureonthe line 4-4 of Fig. 2.

Fig. 5 is .an end view of the casing structure taken. in

projection on the line 5-5 of Fig. 2.

Fig. .6 isa transverse section of the casing structureon the line 6--6of Fig. 2.

Fig. 7 is an end view taken in projection'on .the line 77-of Fig. 1 of aring member to-close'the'outlet ends of the rotor grooves and providedwith a conduit groove 1 for the working medium.

,A further 'objectof the inventiongis to providea casing structurehaving a cooling jacket providing an'efiective and uniform cooling.

.A still further object ofv theinvention is .to providea,..double-'walled casing structuretha-ving a cooling jacket spacebetween its walls, the inner one of said walls 'being relatively thin topromote an efieetive and uniform cooling .of the innerandouter walls .ofthe: casing structure but -yet able to withstand high pressure,differences between the working-chambersof the rotary device and thecooling jacket space thereof. I

According to the ir,1 vention the new casing structure comprises aninner lining andan outer housingsupportingsaid lining, the inner liningcomprisingbarrelportions formed to envelop the-corresponding rotorsections and consisting of a material =too thinfiand insufficient instrength to withstand the gpressure conditions prevailing duringoperation of the device and the outer housing being provided to maintainthe inner lining undeformed inits original shape. I p

Further objects and ,advantageszof the invention will be apparent fromthe followingdescription considered in connection with the accompanyingdrawings which form a .part of this specification, and of which: i

Fig. .l is -a vertical longitudinal section on. the line 11 of Fig. 3through a rotary compressor device provided with a casingstructureconstructed according tothe invention.

in said bores.

Fig. 8 is a horizontal longitudinal section of the ring member ontheline 8-8 of Fig-7.

Fig. 9 is a longitudinal view of one half of the ring member takeninprojection on the line 9 -.-9 of Fig. 7.

Fig. 10 is a detail section of the ring member taken onthelinelO-Jfi ofFig. 7.

.The'casing structure for the compressor has anouter housinglZcomprising two principally cylindrical jacket portions 14 and 16intersecting each otherand providing two intersecting parallel bores 18and 20 fora male and a female rotor, respectively, ofwhich the malerotor'22 is shown in Fig 1, said rotors being provided with intermeshinghelical lobes and grooves and mounted .-in .a manner, which will befurther described below, to rotate The bores 18, 20 areprovided-withinternal projections consisting of annularly disposed fins24 evenly distributed along .the inside of the bores 18,20 and soarranged that thefins .inone of the boresgpass over into thecorresponding fins in the other bore. Said annular fins 24 serve assupporting 'means.for a thinwalled inner lining 26; comprising twobarreltportions 28 and 30, respectively, for each of the bores 18, 20:formed to envelopthecorresponding-rotor. in'its respective bore. Thebarr'el portions 28,,30 of. the lining ;-are provided withannularlydisposed external;projections or fins 32 which are in engagement withthe annular fins .24 on the insidewallof the bores 18, 20 of the-outerhousing 12. The fins 24 of theouter housing :12 are provided each witha-lateral groove 3j4andthe fins 32,0fthe barrel portions 28, 30 of thelining are provided witha corresponding laterallyprotruding tongueportion 36 in keying engagement with the respective groove 34.; Thesefinger portions interlockeach other in oneand the same direction so thatan axialdilatation of the inner-lining 26 in relation to the outer:housing 12 ispermitte'd.

The "barrel portions.2,8 30 are inserted separately in respective bores18, 20 of the housing, the topportions of its fins 24 being cutaway at3810 render the insertion possible and thereafter'the barrel'portionsare turned so that they are brought to seat keyed by the fins'24, 32 engaging each other. When the barrel portions 28, .30 are seatedone pair of the meeting edges of said barrel portions, in theillustrated device the pair 40 at the .top, is welded together while thepair 42 at the bottom is :left free .to permit a perimetral dilatationof thezbarrel per.- tions 28, 30. The centre of the bores for the liningz-in the outerhousingis preferably displaced upwardly a fraction of amillimetre to press thelining upwardxand minimize its displacementdownwardly.

The fins 24 of the bores 18,20 which support the inner lining 26 definea number of annular cooling spaces 44 evenly distributed along thecasing structure and unload'to a high degree the inner lining fromthepressure strains; "the same isXPOSGdtO during the'operation of therotary device. The fins 32 of the lining 26 serveas furtherreinforcements for the lining wallso that the same-can'be made verythinbut yet be able to withstand high'pressure differences between theworking chambers of the rotors ,and the cooling spaces 44 of the caing 3structure. and uniform cooling of the inner and outer walls of thecasing structure. v

According to a preferred construction the housing is made of a lightmetal or of a light metal alloy, such as aluminum or aluminum alloy, andthe lining of a wear and high temperature resistant material, such assteel, in order to obtain a light but nevertheless stable casingconstruction.

The illustrated rotary device has a principally axial inlet 46 for theworking medium which opens into an inlet chamber 48 provided at one end50 of the outer housing 12. Said inlet chamber 48 is in part, at 52,located in the end 50 referred to of the housing 12 and in part, at 54,in an end wall 56 fastened to said end 50 of the housing 12. The ends58of the rotors exposed to the inlet 46 are in part covered by means of ashielding plate 60 to prevent a direct communication between the inletand outlet ducts of the device through any of the grooves of the rotors.For that reason the shielding plate 60 is arranged at the upper half ofthe intersection '62 between the rotor ends and properly displaced inrelation to the direction of rotation ofv the respective rotor.

The inlet chamber 48 surrounds the inlet ends 58 of the rotors annularlyand is provided at its top with an inlet connecting piece 64.

The outlet 66 of the rotary device is radial and located at the top ofthe casing structure toward the opposite end thereof in relation to theinlet end 46. The outer housing has an opening 68 and the inner lining26 an opening 70 for said inlet 66 whichoutwardly ends in a connectionpiece 72. i i

The top portion 74 of the outer housing diverges from the generallycylindrical form it has in its other portions and is raised radiallyupwardly, said top portion 74 being provided with inside longitudinalreinforcing fins 76. As mentioned above, the inner annular fins 24 ofthe outer housing are cut olf at 38 and in order to carry the topintersecting portions 78 (Fig. 6) of the barrels 28, 30 and prevent thecorresponding part of the lining 26 becoming downwardly displaced, thispart ofthe lining is provided with upwardly extending lugs 80 and thetop portion 74 of the outer housing with a downwardly extending lug 82.A stud 84 is inserted through-the lugs to join them together.

To the ends of the rotors, shaft portions 86, 88 are bolted by means ofwhich the rotors are supported-in hub portions 90, 92 of steel or otherhigh temperature and wear resistant material. Said hub portions enclosesuitable bearing and sealing arrangements which, however, form no partof the invention and therefore are not shown in detail.

The hub portions 90 for the rotor shafts 86 at the inlet end aresupported in seats 94 provided in the outer housing itself, said seatsbeing strengthened by radial fins 96 extending as spokes across theannular inlet to the corre sponding ends of the rotors. The surfaces 98of the outer housing fitting closely with the hub portions 90 areprovided with a lining 100 of steel or other high temperature and wearresistant material to protect said surfaces from wear of the assembledparts.

At the outlet end, the rotors end approximately in a plane flush withthe vertical transverse section through the centre of the outlet 66. Thehub portions 92 for the rotor shafts 88 at the outlet end are carried byan internal flange 102 provided on an extension member 104 of the outerhousing formed as a sleeve and bolted to the end 106 of the outerhousing. The surface 108 of the flange 102 fitting closely with the hubportion 92 .is provided with a similar protection lining 110 as thelining 100 for the inlet hub portion 90.

The housing extension member 104 is closed at its outer end by a lid 112through the centre of which is inserted an inlet 114 for a coolingmedium to each rotor. The rotors and their shafts are hollow to form acentral A thin wall of the lining enables an effective cooling channel116'closed' at'the outer end 118 of the shafts 86 at the inlet endanddivided by means of a partition wall 120 in two halves 122, 124. A pipe126 conducts the cooling medium from its inlet 114 to the channel half122 most remote from said inlet 114. A number of radially distributedchannels 128 in the bodies of the rotors conduct the cooling medium backto the channel half 124 most nearly adjacent to the cooling medium inlet114 from which channel half the cooling medium isdischarged throughoutlets 130.

The male and female rotors are provided with synchronizing gears 132located at the ends of the rotor shafts 88 and the rotor shaft 86 of themale rotor is providedwitha connection piece 134 for its attachment to aprime mover..(not shown).

In order to close the grooves of the rotors at their outlet ends a ringmember 136 is provided which is welded to a sleeve 138 guided by theinner lining 26 of the casing structure. The closingring member 136comprises two principally annular half portions 140, 142 concentricallyarranged around respective rotor shafts 88 and the ends of said halfportions 140, 142 which face each other pass over into chord bars 144which are riveted together. The closing ring member 136 is provided atits top with a conduit groove portion or funnel 146 for the workingmedium which faces a circumferentially restricted portion of the outletends of the rotors and communicates with the outlet duct 66 of therotary device.

The sleeve 138 attached to the closing ring member 136 consists of twobarrel halves 148, 150 conformable to the barrel portions 28, 30constituting the inner lining 26. The free end of the sleeve 138 isprovided with 'ofiset fin portions 152, 154 keyed into seats 156, 158 inthe confronting ends of the lining 26 and the housing extension member104.. This arrangement effectively holds the outlet funnel 146 inposition and prevents the deformation of the composite structure ofclosing ring 136 and sleeve 138 at its top.

A number of evenly distributed distance bolts 160 connect the closingring member 136 with the internal flange 102 of the housing extensionmember 104 to further stabilize the construction.

' The outer housing 12' is provided with a base 162 and a number ofannularly and longitudinally disposed external fins 164 and 166,respectively, to further reinforce the housing 12 and to improve theheat transfer to the atmosphere. I The invention also comprises anyrotary device of the type referred to provided with a casing structureas set forth. What is claimed is: l. A housing structure for rotarydevices of the kind having at least two intermeshing rotors withcylindrical envelopes and parallel axes, comprising an inner casingmember having a wall providing cylindrical intersecting barrel portionswith bores and axes corresponding with the envelopes and axes of therespective rotors, and an outer casing member around said inner casingmember and encompassing the latter symmetrically thereto, each twoof'said intersecting barrel portions of said inner casing having onepair of their longitudinal edges fastened together while the otherpairremains free in order to allow expansion of said barrel portions ina circumferential direction, and at least one member of said innercasing and outer casing members being provided with interengaging tongueand groove arrangements having necessary axial clearance in the groovesto provide for the support of the inner casing member in the outercasing member while allowing axial expansion therebe- "tween. 2. Ahousing structure as claimed in claim 1, in which the inner casingmember and the outer casing member are each provided with axially spacedprojections in the form' of annular disposed-ribs provided with axiallydisposed slit and tongue means providing said tongue and groovearrangements for interengagement therebetween in one and the samedirection so as to allow said axial expansion of the inner casing memberrelative'tothe outer casing member.

3. A housing structure as claimed in claim 1, in which the inner casingmember is provided with radially outwardly, and the outer casing memberwith radially inwardly, directed lugs overlapping one another and pinnedtogether.

4. A housing structure as claimed in claim 2, in which the annular ribsof the outer casing member comprise arcuate lengths of lesscircumferential width than the circumferential width of the barrelportions of the inner casing member in order to allow the introductionof said barrel portions and turning of the latter into slit and tongueengagement with the outer casing member.

5. A helical screw device operating with a gaseous medium and comprisinga housing structure having an inlet and an outlet opening disposedadjacent opposite ends, a set of at least two inter-meshing rotors withcylindrical envelopes and parallel axes rotatably mounted in saidhousing structure, said housing structure comprising an inner casingmember enveloping said set of rotors and an outer casing member aroundsaid inner casing member and encompassing the latter symmetricallythereto, the opening adjacent to the high pressure end being defined byprincipally radially directed duct means, in a vertical transverse planeto which the corresponding ends of the rotors terminate in flush, andv acomposite ring element facing said ends of the rotor and including acircumferentially major portion closing said ends of the rotors and acircumferentially restricted minor pertion providing a conduit groovefor the operating me dium and communicating with said radially directedduct means.

6. A helical screw device as claimed in claim 5, in which said compositering element is carried by a composite sleeve structure inserted intoand supported by said-inner casing member.

7. A helical screw device as claimed in claim 6, in which the ends ofsaid composite sleeve structure remote from said composite ring elementis provided with axially disposed fin members and the inner and outercasing members with corresponding slit means to receive said finmembers.

References Cited in the file of this patent UNITED STATES PATENTS1,344,331 Carrey June 22, 1920 1,879,136 Dubrovin Sept. 27, 19321,938,566 Birkigt Dec. 12, 1933 2,041,699 Dahlstrand May 26, 19362,066,788 Lysholm Jan. 5, 1937 2,316,813 Schaper Apr. 20, 1943 2,427,244Warner Sept. 9, 1947 2,510,606 Price June 6, 1950 2,584,899 McLeod ,Feb.5, 1952 2,592,476 Sennet Apr. 8, 1952 2,628,067 Lombard Feb. 10, 19532,755,990 Nilsson et al. a July 24, 1956 FOREIGN PATENTS 486,340 GreatBritain June 2, 1938 644,977 Great Britain Oct. 18, 1950 a 908,254Germany Apr. 5, 1954

